This invention relates to a method and apparatus for subscriber loop disturber recognition.
A number of standards and recommendations have been developed for carrying high speed data on the copper wire subscriber loop that typically connects customer premise equipment (CPE) to a central office (CO). These include digital subscriber loop (xDSL) approaches, such as the asynchronous DSL (ADSL) standard (ANSI T1.413 Issue 2) and the integrated DSL (IDSL) standard (ANSI T1.601-1992) and the high-bit-rate DSL (HDSL) standard (Bellcore TA-NWT-001210 Issue 1, 1991) as well as the symmetrical DSL (SDSL) approach. Other standards for carrying digital signals on copper wire include T1 and G.Lite.
A cable running from a CO typically contains 500 to 1,000 twisted pairs (subscriber loops). The pairs are typically bundled in xe2x80x9cbinder groupsxe2x80x9d. Most cables were designed for voice grade services. In consequence, while the cable itself is shielded and grounded, neither the twisted pairs nor binder groups are shielded and grounded. Because of this, particularly when more than one pair in a binder group carries high speed data, interference (cross-talk) between the data carrying pairs may increase. Interference increases the error rate for data on a pair. To maintain the error rate at an acceptable level (usually 10xe2x88x927 bps), the transmission rate may be reduced to a lower rate. Some data handling approaches, such as ADSL, can automatically adjust the data transmission rate. Others, such as HDSL, cannot. If the transmission rate cannot be automatically adjusted, then whenever the cross-talk noise becomes too high, the transmitter and receiver will be unable to maintain synchronisation. This will result in data disruption, which may profoundly degrade the data rate.
A degraded data rate on a pair could be due to factors other than interference from too many data carrying pairs in a binder group. Thus, when facing a degraded data rate on a given pair, a telephone company (telco) may employ resources investigating other possible sources of the problem (such as a short). Alternatively, the telco may guess from the outset that the degradation is due to too many data carrying pairs in a binder group. If the telco believes this is the problem, the telco will wish to check how many pairs in the binder group to which the given pair belongs carry data. However, with deregulation of local carriers, the telco owning a COxe2x80x94the so-called incumbent local exchange carrier (ILEC)xe2x80x94may not be the telco operating the given pairxe2x80x94the so-called competitive local exchange carrier (CLEC). In such case, neither telco, by itself, is likely to know what service is carried on all pairs running from the CO. Absent full co-operation between telcos, the necessary information may not be readily available. Even without the difficulty of competing telcos, telcos do not keep records as to which pairs are in which binder groups and, further, a telco may have faulty service records for pairs which it is operating.
When a subscriber first requests data service on a subscriber loop, a telco may wish to known the level of interference on the loop from other data carrying loops (i.e., loop disturbers) before implementing the data service. Such a baseline may assist in future diagnostics.
Therefore, there is a need for an approach to determine disturber cross-talk interference in a subscriber loop.
To identify interference in a subscriber loop from other data carrying subscriber loops (i.e., from loop disturbers), a power spectral density sample may be obtained from the subscriber loop under consideration based on at least one measurement while the loop is not transmitting data. The sample power spectral density may then be correlated with each one of a set of one or more known power spectral densities. Each known power spectral density represents a power spectral density in a loop which is not transmitting data in the presence of one of (i) no subscriber loop disturbers, (ii) a particular subscriber loop disturber, and (iii) particular subscriber loop disturbers. Based on the correlations, subscriber loop disturbers may be recognised.
The magnitude of the power in the characteristic power spectral density of a particular type of disturber may be greatest in a frequency band different from that of other types of disturbers. This allows pre-processing of a sampled power spectral density to select likely types of present disturbers. Such pre-processing may reduce overall processing time and increase analysis accuracy. Additionally, in some instances, this pre-processing may sufficiently accurately identify loop disturbers that a correlation operation becomes unnecessary.
Accordingly, the present invention provides a method of subscriber loop disturber recognition, comprising: receiving a sample power spectral density of said subscriber loop based on at least one measurement obtained while said subscriber loop is not transmitting data; correlating said sample power spectral density with each one of a set of one or more known power spectral densities, each known power spectral density in said set being representative of a power spectral density in a loop which is not transmitting data and is in the presence of one of (i) no subscriber loop disturbers, (ii) a particular subscriber loop disturber, and (iii) particular subscriber loop disturbers; based on said correlating, determining present subscriber loop disturbers.
In according to another aspect of the present invention, there is provided a method of subscriber loop disturber recognition, comprising: receiving an identifier for a subscriber loop in a cable; based on said subscriber loop identifier, determining whether customer records for other subscriber loops in said cable are available; if said customer records are available: determining an assumed binder group which includes said subscriber loop based on sequential identifiers for subscriber loops; identifying customer records for subscriber loops of said assumed binder group; for each identified customer record, determining whether an associated service type is a data service; based on said service type determination, determining present subscriber loop disturbers.
In according to a further aspect of the invention, there is provided apparatus for subscriber loop disturber recognition, comprising: means for receiving a sample power spectral density of said subscriber loop based on at least one measurement obtained while said subscriber loop is not transmitting data; means for correlating said sample power spectral density with each one of a set of one or more known power spectral densities, each known power spectral density in said set being representative of a power spectral density in a loop which is not transmitting data and is in the presence of one of (i) no subscriber loop disturbers, (ii) a particular subscriber loop disturber, and (iii) particular subscriber loop disturbers; means for, based on said correlating, determining present subscriber loop disturbers.
In according to a yet further aspect of the invention, there is provided a computer readable medium storing computer executable instructions that when loaded by a computing device, adapt said computing device to: receive a sample power spectral density of said subscriber loop based on at least one measurement obtained while said subscriber loop is not transmitting data; correlate said sample power spectral density with each one of a set of one or more known power spectral densities, each known power spectral density in said set being representative of a power spectral density in a loop which is not transmitting data and is in the presence of one of (i) no subscriber loop disturbers, (ii) a particular subscriber loop disturber, and (iii) particular subscriber loop disturbers; based on said correlating, determine present subscriber loop disturbers.
In according to another aspect of the invention, there is provided a memory for storing information, comprising: a first data structure stored in said memory, said first data structure comprising power spectral density patterns for different loop disturber types singly and in combinations; and a second data structure stored in said memory, said second data structure comprising frequency band indications and associated threshold values for said different loop disturber types.
In according to a further aspect of the invention, there is provided a method of subscriber loop disturber recognition, comprising: receiving a sample power spectral density of said subscriber loop based on at least one measurement obtained while said subscriber loop is not transmitting data; at each of a plurality of frequency bands, comparing an amplitude of said sample power spectral density with a threshold; based on said comparing, determining present subscriber loop disturbers.